LONDON, Engalnd (AFP) — Usain Bolt is targeting a spectacular send-off as the Olympic track and field competition draws to a close on Saturday with Jamaica aiming to seal their sprinting supremacy.

After Bolt completed his unprecedented "double-double" of back-to-back 100m and 200m titles, the Jamaicans are targeting a possible world record as they bid to defend their 4x100m relay crown.

Bolt, who delighted the Olympic Stadium crowd on Thursday with a bravura performance in the 200m, has signalled that the Jamaicans' own world best mark of 37.04sec, set in Daegu last year, could be under threat.

"It could be a world record but you can never say because it's a relay and it's a baton so you never know," Bolt said.

"But for me, we're just going to go out there and enjoy ourselves and run as fast as possible and it will be a good race to close the show again."

Bolt didn't run in Friday's heats, but Nesta Carter, Michael Frater, double sprint silver medallist Yohan Blake and Kemar Bailey-Cole paved the way for him by dominating their heat.

The penultimate day of Olympic competition will see 32 gold medals decided, with track and field highlights including the men's 5,000m, where Britain's Mo Farah will attempt to back up his 10,000m victory, and the women's 800m.

In Saturday's first events, under hot sunshine in the British capital, home favourite Ed McKeever -- dubbed "Bolt in a boat" -- claimed the hosts' 26th gold medal with victory in the men's single kayak sprint

New Zealand's Lisa Carrington won the women's kayak sprint, Russians Yury Postrigay and Alexander Dyachenko snatched the men's double kayak sprint, and Yuri Cheban of Ukraine took gold in the canoe sprint.

Russia's Sergey Kirdyapkin won the gruelling, 50km race walk in 3hr 35min 59sec, embracing his coach with delight as he crossed the line on The Mall, just metres away from Buckingham Palace.

Earlier, the Somalian-born Farah admitted he had struggled to make it through his semi-final following his superb display in the 10,000m.

"My body was a bit tired and I was not as fresh for the 5km as some of the other runners," he said. "I think it showed out there. It wasn't easy out there but I managed to qualify and I'm looking forward to the final."

In the women's 800m final, Caster Semenya will be looking to add the Olympic title to her controversial 2009 world crown.

The race will feature Semenya, defending champion Pamela Jelimo of Kenya and Russia's Mariya Savinova, looking to add Olympic gold to her world title from last year in Daegu.

Jelimo, just 18 when she won gold in Beijing, came to London looking to become the first woman to win the event twice at the Olympics.

Semenya had to undergo drug tests followed by gender tests following her magnificent victory in Berlin at the 2009 worlds, with the athlete complaining of "unwarranted and invasive scrutiny".